The present invention relates generally to electrical insulators and more particularly to a self-monitoring high voltage transmission line suspension insulator for connecting a high voltage transmission line to a transmission line support structure.
Electric power transmission line suspension insulators are subject to damage from causes such as weather conditions and gunfire or other vandalism. A typical insulator in the prior art would contain a central dielectric rod to support the weight of the transmission line. This central dielectric rod must be made of a material having sufficient tensile strength, but such materials, like fiberglass, will lose their dielectric properties when exposed to the environment. For example, water on the surface of such a rod will lead to arcing in the electrical environment of the power line. In time, due to arcing damage, the rod might fail and drop the line. To protect the dielectric rod from the environment, the prior art has employed a dielectric tube to surround the rod. This tube may be made from a plastic or rubber material to have good dielectric properties while exposed to the environment. It should be noted that these materials have inadequate tensile strength to support the transmission line. Some prior art insulators bonded the tube directly to the rod. Other prior art insulators left an annular space between the tube and the rod and filled that space with a dielectric material such as an insulating liquid. Both types of such prior art insulators would be damaged when moisture would enter the tube (and contact the rod) due to gunshot holes or adverse weather conditions. Of course the insulators would be damaged from the gunshots themselves.
The prior art has responded to this problem by helicopter and ground visual inspections of the transmission line insulators. Observers in the helicopters or on the ground try to detect gunfire or other damage. Even with binoculars or other optical aids, this is often very difficult because of the small size of the gunshot hole in the tube and the relatively large distance at which the insulator would be viewed. Moisture penetration damage due to normal wear and tear of the insulator in the environment cannot be detected in this manner until such damage is severe. The goal of the periodic visual inspections is to detect a damaged insulator before it fails and drops a power line.